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Program for modular exponentiation #204

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Merged
swaaz merged 2 commits into from
Oct 10, 2020
Merged

Program for modular exponentiation #204

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d011262
Code for modular-exponentiation
Kunal888 Oct 10, 2020
831c0d2
Updated README.md for Program-15
Kunal888 Oct 10, 2020
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42 changes: 42 additions & 0 deletions C++/Program-15/program.cpp
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/*
* Code for modular exponentiation
* Time complexity : O(n*log(n))
*/

#include<bits/stdc++.h>
using namespace std;

// This function returns value of (x^y)%mod.
int power(int x, int y, int mod)
{
int answer = 1; // Initialise the answer

x = x % mod;

if(x == 0) return 0; // If x is divisible by mod

while(y > 0)
{
if(y % 2 == 1) // If y is odd multiply x with answer
{
answer = (answer*x) % mod;
}

y /= 2; // reduce the value of y
x = (x*x) % mod; // increment the value of x
}

return answer;
}


// Main function
int main()
{
int x = 2, y = 10, mod = 1000000007;
int result = power(x, y, mod);
cout << result << '\n';

return 0;
}
1 change: 1 addition & 0 deletions C++/README.md
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Expand Up @@ -10,3 +10,4 @@
| Program-08 | Program to reverse a string |
| Program-09 | Program to check if two numbers are equal without using arithmetic operators or comparison operators.
| Program-10 | Program to find the missing number in a Sorted Array.
| Program-15 | Program to find modular exponentiation.